2. ICU's Windows-949 has 190 additional round-trip mapping entries. Most of
them (188 of them) are for the two user-defined blocks in KS X 1001 (in
EUC-KR, "C9 [A1-FE]" and "FE [A1-FE]") that are mapped to PUA code points
(U+E000 - U+E0BB). The remaining two are U+0080 and U+F8F7 mapped to 0x80 and
0xFF.

I don't think that we want to support the two user-defined blocks in KS X 1001.
I'm not sure about U+0080 and U+F8F7.

However, I believe that quite many (NOT all) of 'decoding only' entries had
better be supported.